Electrical connectors used in many of today's products such as those described above must provide high electrical performance, high density and highly reliable connections between various circuit devices, which form important parts of these products.
Improvement of signal integrity (performance) for such connectors may be accomplished by providing the interconnections with shielding, thus helping these to more closely match the desired product's impedance. To enable effective repair, upgrade, and/or replacement of various components of the product (e.g., connectors, cards, chips, boards, modules, etc.), it is also highly desirable that such connections be separable and re-connectable in the field. Such a capability is also desirable during the manufacturing process for such products in order to facilitate testing, for example. Both of these features (shielding and separability) must be provided in such a manner so as to assure a final product which is highly reliable and cost effective. In this regard, it is understood that one or more misconnections within critical parts of the overall product may result in product failure and the need for costly replacement.
A land grid array (hereinafter also referred to as an LGA) interposer connector (hereinafter also simply referred to as an interposer) is an example of such a connector in which each of two primarily parallel circuit elements to be connected has a plurality of contact points, arranged in a linear or two-dimensional array. An array of interconnection elements (the LGA interposer) is placed between the two arrays to be connected, and provides the electrical connection between the contact points or pads. An LGA interposer typically includes at least one conductive plane sandwiched between two dielectric planes. The conductive plane typically includes a pattern of circuitry. A plurality of plated through holes (hereinafter also referred to as PTH's) are formed through the planes of the interposer so that the pattern of plated through holes formed on one surface of the interposer matches the pattern of ground, power and signal sites on the chip carrier or other electrical component; and the pattern of plated through holes on the opposite side of the interposer matches the pattern of ground, power, and signal sites on the PCB or other circuitized substrate. Examples of LGA and similar interposers are known in the art, with examples provided below. It is to be understood that the invention is not limited to LGA connectors but is applicable to many other kinds of connectors and modules.
In U.S. Pat. No. 6,954,984, there is described an Land Grid Array structure which includes a flexible film interposer that provides electrical connection between a multi-chip module and the next level of integration such as a system board while allowing for engineering change capabilities as well as a means for decoupling power to ground structure to minimize switching activity effects on the overall system using this structure.
In U.S. Pat. No. 6,638,077, there is described a shielded carrier with electrical components, resulting in an LGA interposer connector with apparent improved electrical performance and enhanced functionality. The carrier includes components such as resistors and capacitors on and/or in the carrier. The components are preferably of the surface mount variety or are imbedded within the carrier, due to the inherent lower profile of these form factors. Decoupling capacitors and terminating resistors are two examples of components that may improve performance.
In U.S. Pat. No. 6,528,892, there is described a flexible chip carrier with contact pads on its upper surface matching those of the chip with the pads conductively connected to LGA pads on its lower surface matching those of a PCB. The chip carrier is provided with a stiffening layer at the LGA interface which is mechanically attached to the lower surface of the chip carrier. Holes are formed in the stiffening layer to expose the LGA pads. The holes are then filled with a conductive adhesive material. Compliant LGA bumps are applied to the uncured conductive adhesive material and the material is then cured.
In U.S. Pat. No. 6,471,525, there is described a carrier with electrical shielding of individual contact elements, resulting in an LGA interposer connector with alleged improved electrical performance. The carrier includes a plurality of openings, each of which may contain an individual contact element. The openings may be plated with conductive material, and may also be commoned to one or more reference voltages (e.g., ground) present on at least one conductive layer of the carrier. The carrier may be a single unified structure with a conductive layer on one outer surface, or much more complex, having many layers of dielectric and conductive material.
In U.S. Pat. No. 6,312,266, there is described a carrier that provides improved retention to the individual contact elements resulting in an LGA interposer connector with apparent improved mechanical and electrical performance. In one embodiment, the carrier, which includes upper and lower sections of dielectric material with an adhesive layer in between, includes a plurality of openings, each of which may contain an individual contact element. During assembly of the connector, once the contact elements are inserted, the adhesive layer is reflowed, thereby allowing the carrier to capture the location of the contact elements both with respect to each other as well as to the carrier. Alternately, the carrier may be implemented in a manner which, while not including an adhesive layer to be reflowed, still provides improved retention of the individual contact elements.
In U.S. Pat. No. 6,137,161, there is described a semiconductor package which includes an interposer with upper surface contacts aligned with circuit chip contacts and lower surface contacts aligned with the corresponding contacts on a supporting substrate. The interposer includes a series of ground plane layers which are capacitively coupled to the conductors that connect the upper surface contacts to the lower surface contacts. The ground plane layers closest to the circuit chip have plates there-between and electrically separated there-from which are connected to the power input supply lines to form decoupling capacitances. The ground plane layers more remote from the circuit chip have, there-between and electrically separated there-from, conductive flange portions attached to individual signal lines to form a low pass feed-through filter for each signal line. The capacitance of the flange portions is designed to establish the correct roll off to pass the desired signals and shunt to ground the unwanted harmonics while the decoupling capacitance is sized to afford the required, stabilized power supply. The semiconductor package also may include a conductive shield member that surrounds the top and four sides of the package and is connected to the grounded elements of the interposer to provide mechanical connection and apply ground potential to the shield.
In U.S. Pat. No. 6,097,611, there is described an LGA carrier which includes an interposer having a first surface and a second surface opposite the first surface, with a plurality of locations on the first surface adapted to receive a plurality of semiconductor dice and passive components. The second surface has a plurality of conductive pads coupled thereto.
In U.S. Pat. No. 6,097,609, there is described an electronic packaging assembly in which an electronic component is disposed on a socketing substrate utilizing a ball grid array or LGA. The socketing substrate contains a series of pins that are embedded within the thickness of the socketing substrate, these pins corresponding to the ball grid array or land grid array contacts of the electronic component. The socketing substrate is mounted onto a motherboard using an array of solder balls that correspond to and are disposed on, the end of the pins facing the motherboard. If desired, the electronic component may be protected by a metal lid.
In U.S. Pat. No. 5,599,193, there is described an electrical interconnector for connecting an integrated circuit or other electrical or electronic component to a circuit board or for interconnecting two or more circuit boards. The interconnector comprises a substrate having one or more resilient elements of a non-conductive material and having opposite contact surfaces. A flexible conductive coating is provided on the contact surfaces of the resilient elements and extends between the contact surfaces to provide electrical connection there-between. In one embodiment, each element is integrally formed with a resilient substrate and has electrically conductive contact surfaces which are outward of the respective substrate surfaces and are electrically connected through a conductive surface which extends through vias (openings) formed in the substrate. In another embodiment, each element is individually formed and is disposed within a corresponding cavity of a separate substrate. In a further embodiment, each element is individually formed having different sections of different durometers so as to provide intended spring or resilience characteristics. A particulate layer can be provided on the conductive contact surfaces to provide a roughened surface by which an oxide layer on a mating electrical contact is penetrated to minimize contact resistance.
In U.S. Pat. No. 5,530,288, there is described an interposer including a first face and second face opposite the first face and at least one electrically conductive plane. The conductive plane functions as a power, ground, or signal plane. At least one electrically insulating plane is positioned on opposite sides of the conductive plane. A plurality of PTH's are formed through the conductive plane and the two insulating planes. The PTH's are selectively electrically joined to the conductive plane. At least one passive electronic structure is positioned within the interposer structure.
As understood from the following description, the present invention provides an interposer with improved shielding of various conductors therein in a new and unique manner and which can be produced using conventional PCB manufacturing processes which require little or no modification thereto. It is believed that such an invention will constitute a significant advancement in the art.